Agronomic Effectiveness of Partially Acidulated Phosphate Rock

Laboratorial incubation and field experiments were conducted on soils ranging in texture from sandy loam to clay and in pH from 3.6 to 9.0 to determine the agronomic effectiveness of single superphosphate (SSP).fused magnesium phosphate(FMP) and partially acidulated phosphate rock(PAPR) on 8 field crops.The results showed that the pattern of available P released from SSP was fixing-releasing-fixing-steady state,while that of PAPR was shortly fixing-slowly releasing-fixing steady state.And the PAPR,SSP and FMP were equally effective as judged by yield Puptake by phants and extractable P in soils after crop harvesting,The PAPR used as basal fertilizer was more effective than that as top dressing,and its residual effect was also obvious.     

Adsorption of Phosphate on Variable Charge Soils

The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing.     

Promoting Growth,Yield, and Phosphorus-Use Efficiency of Crops in Maize–Wheat Cropping System by Using Polymer-Coated Diammonium Phosphate

Field experiments were conducted at Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan, to check the effect of polymer-coated diammonium phosphate (DAP) on maize–wheat cropping system. Different rates of polymer-coated and uncoated phosphorus (P) were applied first to maize then followed by wheat after harvesting of maize on same field. Results showed that application of 100% of recommended P from polymer-coated DAP increased plant height (10%), chlorophyll content (4%), biological yield (17%), grain yield (36%), agronomic efficiency (43%), and nitrogen, phosphorus, and potassium contents of maize produces, while in case of wheat 75% recommended P from polymer-coated DAP increased plant height (6%), chlorophyll content (18%), biological yield (20%), grain yield (14%), agronomic efficiency (72%), and nitrogen, phosphorus, and potassium contents of grains and straw as compared with uncoated DAP. So, it can be summarized that polymer-coated DAP can effectively improve growth, yield, and phosphorus-use efficiency of maize and wheat crop.     

Transformation of Phosphate Fertilizers with Different Solubilities in Calcareous Soils

In this research work,the authors,using the recently developed method of fractionating the forms of inorganic phosphorus in calcareous soils,have studied the transformation processes of inorgnic phosphorus in three different phosphate fertilizers,i.e.,superphosphate,diammonium phosphate and calcium magnesium phyosphate,being commonly used in China,during a period of 3 years after their application to calcareous soils,and based on the experimental results obtained,some problems in current use of phosphate fertilizers are discussed.     

Dolomite Phosphate Rock–Based Slow-Release Fertilizer for Agriculture and Landscapes

Most soils in Florida are very sandy, and water-soluble fertilizers (WSF) are subjected to leaching loss. Alternate fertilization is a promising practice to reduce such loss. Dolomite phosphate rock (DPR), which contains calcium, magnesium, and phosphorus, is potentially useful for agricultural production and landscaping plants. In this study, DPR fertilizers were developed from mixing of DPR material and N-viro soil. A typical agricultural soil (Alfisol) in Florida was used for greenhouse studies, and ryegrass and citrus seedlings were tested. The DPR fertilizers appeared superior to WSF for the growth of ryegrass based on dry-matter yield and nutrient concentrations in plant; however, it was not evident in citrus seedlings. DPR fertilizers were effective in raising pH (by 3 units) and electrical conductivity of acidic sandy soils and increasing soil organic matter, total nutrients, and available nutrients. The concentrations of copper, lead, and zinc in the plant tissues were less than toxicity limits.     

Types of Crystalline Iron Oxides and Phosphate Adsorption in Variable Charge Soils

The types,contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorption on the clay fractions in soils with varable charge in southern China were investigated by means of XRD,TEM,EMA and chemical analysis methods.Results indicated that the types and contents of crystalline Fe oxides varied with the soils examined.The dominant crystaline Fe oxide was hematite in the latosols and goethites in the red soils.In yellow-brown soils,the only crystalline Fe oxide was goethite.The difference between Ald and Alo came mainly from the Al Substituting for Fe in the Fe oxides.The crystal morphology of goethite appeared mainly as subrounded flat or iso-dimensional rather than acicular particles,Hematities occurred in plates of various thickness,Their MCDa/MCDc ratios in the latosols and red soils were generally above 1.5 and below 1.5,respectively.The MCD values of goethites and hematites were 15-25nm and 20-35nm,and their specific surface areas were 80-120m^2/g and 35-75m^2/g,respectively.The goethite crystals were generally smaller,Variations of the total amounts of crystalline Fe oxides in clay fractions were not related to plhophats adsorption.The types,contents and morphologies of crystalline Fe oxides in the soils remarkably affected phosphate adsorption characteristics of the soils.The phosphate adsorption of goethite was much greater than that of hematite,The higher th MCDa/MCDc ratio of hematite,the lower the phosphate adsorption.     

Ameliorative Effects of Potassium Phosphate on Salt‐Stressed Pepper and Cucumber

Abstract

Bell pepper (Capsicum annuum cv. Urfa Isoto) and cucumber (Cucumis sativus cv. Beith Alpha F1) were grown in pots containing field soil to investigate the effects of supplementary potassium phosphate applied to the root zone of salt‐stressed plants. Treatments were (1) control: soil alone (C); (2) salt treatment: C plus 3.5 g NaCl kg^?1 soil (C + S); and (3) supplementary potassium phosphate: C + S plus supplementary 136 or 272 mg KH₂PO₄ kg^?1 soil (C + S + KP). Plants grown in saline treatment produced less dry matter, fruit yield, and chlorophyll than those in the control. Supplementary 136 or 272 mg KH₂PO₄ kg^?1 soil resulted in increases in dry matter, fruit yield, and chlorophyll concentrations compared to salt‐stressed (C + S) treatment. Membrane permeability in leaf cells (as assessed by electrolyte leakage from leaves) was impaired by NaCl application. Supplementary KH₂PO₄ reduced electrolyte leakage especially at the higher rate. Sodium (Na) concentration in plant tissues increased in leaves and roots in the NaCl treatment. Concentrations of potassium (K) and Phosphorus (P) in leaves were lowered in salt treatment and almost fully restored by supplementary KH₂PO₄ at 272 mg kg^?1 soil. These results clearly show that supplementary KH₂PO₄ can partly mitigate the adverse effects of high salinity on both fruit yield and whole plant biomass in pepper and cucumber plants.     

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

In this study, an iron?Czirconium binary oxide with a molar ratio of 4:1 was synthesized by a simple coprecipitation process for removal of phosphate from water. The effects of contact time, initial concentration of phosphate solution, temperature, pH of solution, and ionic strength on the efficiency of phosphate removal were investigated. The adsorption data fitted well to the Langmuir model with the maximum P adsorption capacity estimated of 24.9?mg P/g at pH?8.5 and 33.4?mg P/g at pH?5.5. The phosphate adsorption was pH dependent, decreasing with an increase in pH value. The presence of Cl^?, SO ₄ ^2? , and CO ₃ ^2? had little adverse effect on phosphate removal. A desorbability of approximately 53?% was observed with 0.5?M NaOH, indicating a relatively strong bonding between the adsorbed PO ₄ ^3? and the sorptive sites on the surface of the adsorbent. The phosphate uptake was mainly achieved through the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. Due to its relatively high adsorption capacity, high selectivity and low cost, this Fe?CZr binary oxide is a very promising candidate for the removal of phosphate ions from wastewater.     

Species of Inorganic Phosphate Solubilizing Bacteria in Red Soil and the Mechanism of Solubilization

INTRODUCTION The insoluble phosphates which can not be directly absorbed by plants are the mai forms of inorganic phosphate in soil. These kinds of phosphates can be solubilized by several species of bacteria which are widely spread in soil especially in rhizosphere where70% of the bacteria are capable of solubilizing inorganic phosphate.     

Application of Ground Phosphate Rock to Dimmish the Effects of Simulated Acid Rain on Soil Properties

The effects of simulated acid rain retained in soil on the properties of acid soil and its diminishing by application of ground phosphate rock were investigated by using the sorption method.Results show as follows:(1)For yellow brown soil,the effect of simulated acid rain on the properties of soil with a pH value of 5.9 was relatively small,except a great quantity of acid rain deposited on it.(2) for red soil,the effect of simulated acid rain on the properties of soil was significant.With the increase of the amount of acid deposition,the pH value of soil was declined,but the contents of exchangeable H^ ,Al^3 and Mn^2 and the amount of SO4^1- retention were increased.(3) Many properties of acid soils could be improved by applying ground phosphate rock.For example,pH value of soils and the amounts of available P and exchangeable Ca^2 and Mg^2 were increased,and the amounts of exchangeable H^ and Al^3 and SO4^2- retained was reduced.The application of ground posphate rock could effctively diminish the pollution of acid rain to soil.     

Effects of Organic Anions on Phosphate Adsorption and Desorption from Variable—Charge Clay Minerals and Soil

Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite,goethite,amorphous Al-oxide and Ultisol were studied.P adsorption was significantly decreased as the concentration of the organic anions increased from 10^-5 to 10^-1 M.At 0.1 M and pH 7.0,tartrate decreased P adsorption by 27.6%-50.6% and citrate by 37.9-80.4%,depending on the kinds of adsorbent.Little Al and/or Fe were detected in the equilibrium solutions,even at the highest concentration of the organic anions.Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given gonditions. Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KCl solution alone.However,for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P.The effect of organic anions on phosphate desorption arises primarily from ligand exchange.     

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

Abstract

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg^?1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H₂O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H₂O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=At^B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.     

Rice Yields Enhanced through Integrated Management of Cover Crops and Phosphate Rock in Phosphorus‐deficient Ultisols in West Africa

The relatively low solubility and availability of phosphorus (P) from indigenous phosphate rock could be enhanced by legumes in the acid soils of humid forest agroecosystems. Crotalaria micans L. was grown in a screenhouse without P or with P from triple superphosphate (TSP) and Malian Tilemsi Rock P. The P response of 20 cover crops was field‐evaluated using TSP and Rock P. In both experiments, the fertilized cover crops were followed by upland rice without mineral N or P application. Mean rice grain yield and agronomic residual P‐use efficiency were similar for both P sources. In the field, 1‐year fallow treatment of Canavalia ensiformis (velvet bean) supplied with Mali Rock P gave the highest rice grain yield of 3.1 Mg ha^?1, more than 180% that of 2‐year continuous unfertilized rice (cv. ‘WAB 56‐50’). Among continuous rice plots, ‘NERICA 2’ (interspecific rice) supplied with Rock P produced the highest yield (2.0 Mg ha^?1), suggesting that ‘NERICA 2’ might have greater potential to solubilize rock P. Results indicate that when combined with an appropriate legume, indigenous rock‐P can release sufficient P to meet the P requirement of the legume and a following upland rice crop in rotation.     

Glycine–Glomus–Phosphate Solubilizing Bacteria Interactions Lead to Fertilizer Phosphorus Economy in Soybean in a Himalayan Acid Alfisol

Effects of Glycine–Glomus–phosphate solubilizing bacteria (PSB) interactions were studied on productivity, nutrient dynamics, and root colonization in soybean in a phosphorus (P)–deficient Himalayan acidic Alfisol in a greenhouse experiment. Treatments consisted of three vesicular arbuscular mycorrhizae (VAM) cultures, VAM_L [VAM culture, Glomus mosseae, developed by CSK Himachal Pradesh Agricultural University, Palampur, India], VAM_T [VAM culture, Glomus intraradices, developed by Centre for Mycorrhizal Research, The Energy and Resources Institute (TERI), New Delhi, India], and VAM_I [VAM culture, Glomus mosseae, developed by Indian Agricultural Research Institute (IARI), New Delhi, India], and a local PSB culture (Pseudomonas striata) alone or in combination with or without 75% of recommended phosphorus pentoxide (P₂O₅) dose based on targeted yield concept following the soil-test crop response (STCR) precision model. Sole application of PSB or either of the above VAM cultures considerably enhanced VA-mycorrhizal root colonization and root weight besides crop productivity and nutrient uptake over control. A similar stimulatory effect with significant enhancement on mycorrhizal root colonization and root weight was observed with coinoculation of PSB and VAM cultures over the control. Dual inoculation of VAM and PSB cultures also resulted in significant improvement in grain and straw yield besides grain protein content, thereby revealing a synergistic interaction between VAM and PSB. Coinoculation with either of VAM_T (Glomus intraradices) or VAM_I (Glomus mosseae) + PSB + 75% P₂O₅ dose remained at par with sole application of 100% P₂O₅ dose with respect to crop productivity, nutrient content, nutrient uptake, and soil fertility status besides the greatest root colonization and root weight at flowering, indicating that Glycine–Glomus–PSB interactions in combination with 75% P₂O₅ dose based on STCR precision model lead to economization of fertilizer P by about one-fourth without impairing crop productivity and soil fertility in soybean in a Himalayan acidic Alfisol.     

Response of ‘Jonagold’ Apple Trees in the First Three Years after Planting to Mono-Ammonium Phosphate Fertilization Under Replant Problem Conditions

Abstract

The objective of the experiment was to examine response of immature apple trees to application of mono-ammonium phosphate (MAP) fertilizer on replant problem soil. The study was carried out during 2001–2003 under a greenhouse on ‘Jonagold’ apple trees/M.9 EMLA planted singly in 50 L polyethylene containers filled with a sandy loam soil with low status of both organic matter and phosphorus (P) in soil solution. This soil originated from an apple orchard unfertilized with P for 23 years. The biological test showed the presence of specific replant disease in the soil. Immediately before apple tree planting, the soil was mixed with MAP at rates of 1, 2, and 3 g L^{? 1}. Trees grown in the soil untreated with MAP served as a control. Each year apple trees were drip-irrigated and supplied with nitrogen (N) at differentiated rates to achieve a level of 50 g N per plant. The results showed that MAP application increased soil solution P status. Simultaneously, MAP supply at rates of 2 and 3 g L^{? 1} caused a drop in soil pH value in the last two years of the experiment. MAP treatments increased both dry weight and length of fine roots (< 2 mm in diameter), vigor of trees, the number of flower clusters per tree, flower intensity, the number of fruits per tree, and P concentrations in leaf and fruit tissues. Fruits from MAP-supplied trees were firmer than those of the control trees. Mean fruit weight, titratable acidity, and soluble solids concentration of ‘Jonagold’ apples at harvest were not influenced by MAP treatment. Fruits from MAP-supplied apple trees had increased calcium concentration only in one year. It is concluded that pre-plant application of MAP at a rate of 1g L^{? 1}can be recommended on coarse-textured soils with low P status in soil solution to increase precocity of apple trees. However, MAP-supplied apple trees have to be watered to avoid the risk of osmotic stress.     

Evaluation of Dolomite Phosphate Rock–N‐Viro Soil Mixtures for Growth of a Horticultural Crop in an Acidic Sandy Soil

Abstract

Most agricultural soils in the Indian River area, South Florida, are sandy with minimal holding capacity for moisture and nutrients. Phosphorus (P) leaching from these soils has been suspected of contributing to the eutrophication of surface waters in this region. Dolomite phosphate rock (DPR) and N‐viro soil are promising amendments to increase crop production and reduce P loss from sandy soils. Soil incubation and greenhouse pot experiments were conducted to examine the effects of Florida DPR–N‐viro soil mixtures on the growth of a horticultural crop in an acidic sandy soil and to generate information for developing a desired formula of soil amendments. Dolomite phosphate rock and N–viro soil application increased soil pH, electrical conductivity (EC), extractable P, calcium (Ca), and magnesium (Mg). N–viro soil had greater effect on soil pH, organic matter content, and microbial biomass than the DPR. Comparatively higher nitrification rates were found in the N–viro soil treatment than the DPR treatment. A systematic decrease in soil‐extractable P was found with increasing proportions of N‐viro soil from the combined amendments. Greenhouse study demonstrated that the application of DPR and N‐viro soil significantly improved dry‐matter yield and increased plant P, Ca, and Mg concentrations of radish (Raphanus sativus L.). Based on dry‐matter yield and plant N uptake, the combined amendments that contained 30% or 20% of DPR materials appear to be optimal but remain to be confirmed by field trials.     

氮素形态, 光合作用, 光呼吸

Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and photorespiration. However, there is no consistent evidence of a specific mechanism that could explain the plant growth reduction under ammonium supply. It is generally accepted that during the light reaction, a surplus of nicotinamide adenine dinucleotide hydrogen phosphate （NADPH） is produced, which is not completely used during the assimilation of CO2, Nitrate reduc- tion in the leaf represents an additional sink for NADPH that is not available to ammonium-grown plants. Nitrate and ammonium nutrition may use different pathways for NADPH consumption, which leads to differences in photosynthesis and photorespiration. The morphological （i.e., cell size, mesophyll thickness, and chloroplast volume） and enzymic （i.e., ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco）, phosphoenolpyruvate carboxylase （PEPCase）, and glutamine synthetase/glutamate synthetase （GS/GOGAT）） differences that develop when plants are treated with either nitrate or ammonium nitrogen forms are related to photosynthesis and photorespiration. The differences in photorespiration rate for plants treated with nitrate or ammonium are related to the conversion of citrate to 2-oxoglutarate （2-OG） and photorespiratory CO2 refixation.